1. Field of the Invention
The present invention pertains to a bearing and lubrication system for use in scroll fluid devices. The bearings utilized are hydrostatic/hydrodynamic in nature yet permit sufficient leakage for lubricating relative rotatable members of the scroll fluid device.
2. Related Background Technology and Art
Scroll fluid devices are known which comprise a pair of opposed meshed axially extending involute wrap elements which co-rotate and are supported for orbital motion relative to each other to create radially moving progressively and periodically varying volume fluid transporting chambers between the wrap elements. When the involute wrap elements are rotated at high speeds within a housing to expand or compress a fluid medium, a considerable amount of axial and radial force tending to separate the spiral wraps is generated. In order for the scroll fluid device to operate, these axial and radial forces must be opposed. In addition, a sufficient amount of lubricating fluid must be provided between the relatively rotating parts of the scroll fluid device to minimize wear and to prevent excessive operating temperatures resulting from friction.
It is known in the prior art to provide fluid bearings in order to counteract these axial and radial forces developed in high speed scroll fluid devices. In U.S. Pat. No. 4,993,929, for example, a scroll-type machine is disclosed which incorporates a self-pressurizing hydrostatic thrust bearing used to maintain a constant interface of oil between the axial thrust surfaces of the scroll elements and the housing. As stated in the patent, the oil film thickness in the thrust bearing chambers are on the order of 1 mil in order to prevent dissipative action of the oil from this high pressure chamber to the surrounding low pressure areas. In such a system, a separate lubrication circuit must be provided in addition to the fluid circuit used to supply the thrust bearings since the bearing chamber arrangements are designed to prevent the dissipation of oil therefrom. This auxiliary lubrication system supplies a lubricating film layer between the relative rotatable parts of the scroll fluid device and housing.
In U.S. Pat. No. 4,874,302, a scroll fluid compressor is disclosed which includes a hydrodynamic thrust bearing interposed between an orbiting scroll member and a bearing support which not only functions to provide axial reactive force to the orbiting scroll member but also admits lubricating fluid into guiding grooves associated with the synchronizer used between the intermeshed scroll members. In the '302 patent, the scroll type compressor includes one fixed scroll member and a second orbiting scroll member. In general, the oil film thickness in such known hydrodynamic thrust bearings is typically quite small, on the order of 1 mil. If this type of bearing arrangement was utilized in a high-speed, high output, co-rotating scroll compressor, it could not adequately counteract the axial thrust forces developed and would result in excessive power losses at high speed and high oil temperatures. Since the oil film thickness in typical hydrodynamic thrust bearings is quite small, a very stiff and massive bearing plate having a large oil film surface area is usually required. In a high-speed co-rotating scroll environment, a large massive bearing plate can create efficiency losses due to the power required to rotate the plate as well as vibrational problems.
Therefore, a need exists for a thrust bearing arrangement for use in a high-speed, co-rotating scroll fluid device which not only can adequately counteract the radial and axial forces developed during operation of the scroll device but which can be used with a single oil supply system which provides lubrication between the relatively rotating parts of the scroll fluid device. In addition, there exits a need for a thrust bearing and lubrication system which will maintain operating stability and will enhance operating efficiency.